In the opening paragraph of Maps for Lost Lovers, Nadeem Aslam writes: "The snow storm has rinsed the air of incense... but it is there even when absent, drawing attention to its own disappearance." There, though we don't know it at the time, is the very heart of the novel. The lovers, Chanda and Jugnu, have disappeared from the English town of Dasht-e-Tanhaii, and though they have been gone five months when the book opens, they haunt it, and the lives of those who occupy it, until the final pages.

The English town of Dasht-e-Tanhaii? It sounds more like something out of a fairytale than a place off the M4. But no, it is a town with a large community of Pakistani migrants who have renamed their new home Dasht-e-Tanhaii: The Wilderness of Loneliness or The Desert of Solitude. Aslam has populated this place with a remarkable cast: Jugnu's brother, Shamas, a gentle, liberal man with no time for the orthodox form of Islam to which so many in his community cling; Shamas's sons and daughter, part of the generation that must attempt to forge a link between the Pakistani and British parts of their lives without being consumed by anger or pulled apart by conflicting demands; Suraya, who was "mistakenly" divorced by her husband in Pakistan while he was in a drunken rage, and now (by the precepts of the Islamic sect she follows) must find someone else to marry and divorce her before she can return to her former husband and their son.

But the most extraordinary of the characters is Shamas's wife, Kaukub. A woman brought up to believe in an unforgiving, narrow-minded version of Islam, she could, in the hands of a lesser novelist, have become a monster. But in Aslam's hands she is transformed into a woman entirely human, entirely heartbreaking. She is the devoted mother behind the headlines about the parent who sends her British-born-and-raised child back to Pakistan into an arranged marriage; she is the young bride who used to step out of the bath and wake up her husband by twisting her hair into a yard-long rope and letting beads of water fall over him, but then grew into a woman who equates sex with shame and sin; she is the voice of condemnation raised against all transgressions from orthodoxy and also the voice telling us: "Islam said that in order not to be unworthy of being, only one thing was required: love."

In this book, filled with stories of cruelty, injustice, bigotry and ignorance, love never steps out of the picture - it gleams at the edges of even the deepest wounds. Perhaps this is why the novel never gets weighed down by all the sorrows it carries: there is such shimmering joy within it, too. Here are characters hemmed in on one side by racism and on the other side by religious obscurantism, and yet they each carry remarkable possibilities within them.

But the beauty in the novel does not just come from within the characters. As much as anything else, Maps for Lost Lovers is a homage to the flora and fauna of an English town. Writing about violent racist attacks on the homes of migrants, Aslam tells us: "At night the scented geraniums were dragged to the centre of the downstairs room in the hope that the breeze dense with rosehips and ripening limes would get to the sleepers upstairs ahead of the white intruders who had generated it by brushing past the foliage in the dark after breaking in." Throughout the book, birds and flowers and insects make their way into the prose, either pulling someone out of a bleak thought or, as in the lines above, heightening a vicious moment through the shock of contrast. To read Aslam's physical descriptions is to be reminded of the ability of language to make us re-see the world through analogy and metaphor. So, a woman's gold bracelet is composed of a series of semi-colons; dead tulips lean out of a bin like the necks of drunk swans; a falling icicle is a radiant dagger. Perhaps the words that best describe the remarkable achievement of this novel come from within its pages, in a glorious riff on the wonders of jazz musicians: "[They] seemed to know how to blend together all that life contains, the real truth, the undeniable last word, the innermost core of all that is unbearably painful within a heart and all that is joyful, all that is loved and all that is worthy of love but remains unloved, lied to and lied about, the unimaginable depths of the soul where no other can withstand the longing and which few have the conviction to plumb, the sorrows and the indisputable rage."